Field
The present application relates to an optical system of a stereo video endoscope with lateral viewing direction, comprising a sideways looking distal optical assembly and a proximal optical assembly, wherein the distal optical assembly comprises successively in a direction of light incidence an entrance lens, an optical deflection unit and an exit lens, embodied as a hollow positive meniscus, on a common optical axis, wherein the distal optical assembly has at least in sections two right and left lens system channels of identical type and arranged parallel to one another, having in each case a dedicated optical axis, which have in each case in the direction of light incidence at least one first lens and an achromatic lens group, as well as a corresponding stereo video endoscope with lateral viewing direction.
Prior Art
The use of stereoscopic optical systems in endoscopes is currently limited due to the required installation size on straight-ahead looking endoscopes, i.e. on endoscopes with a so-called 0° viewing direction.
A system of a sideways looking stereoscopic endoscope, which has a distal and a proximal optical assembly, is known from U.S. Pat. No. 5,689,365 A. The distal optical assembly is arranged distally behind a tilted entrance window and comprises a plano-convex entrance lens, which sits on a prism deflection unit, in which the tilted optical axis of the system is deflected in the direction of the longitudinal extension of the shaft of the endoscope. A raised positive meniscus lens is arranged at the exit of the prism unit as an exit lens of the distal optical assembly. The proximal optical assembly follows proximally. While the distal optical assembly is connected in a rotationally fixed manner with the jacket tube, the proximal optical assembly is rotatably arranged in the jacket tube in order to enable a change in the viewing direction.
The proximal optical assembly comprises two lens channel systems, namely respectively for the right image and the left image separately, in which respectively one biconvex entrance lens as well as one achromatic group embodied as a doublet are arranged. Two image sensors are connected in a torque-proof manner with this rotatable proximal optical assembly and receive the separate left and right images.
Other different optical systems, which function in a similar manner, are introduced in U.S. Pat. No. 5,689,365 A, wherein for example relay lens sets are also used in order to direct the incident light into the handle of an endoscope and to the image sensors arranged there.
The optical system introduced in U.S. Pat. No. 5,689,365 A realizes a stereo base of less than 1.1 mm with an outer diameter of the endoscope shaft of more than 15 mm. This means that it is not suitable for an endoscopic use due to its diameter and the achievable three-dimensional effect is not large enough. Furthermore, so-called 3D distortions are not corrected sufficiently in the optical system.
With specific reference to FIG. 1 of U.S. Pat. No. 5,689,365, the shows a known stereo video endoscope from the state of the art in a cross-sectional representation. The stereo video endoscope 1 comprises an endoscope shaft 2 and a handle 3. In an outer jacket tube 12, an optical fiber bundle 13 for illuminating the operative field is arranged distal to the endoscope shaft 2, which ends in the handle 3 in a fiber optic connection 4.
In an inner jacket tube (without reference number), a distal optical assembly 14, which has a plano-concave entrance lens 14b, a prism deflection unit 14c and an exit lens 14d embodied as a hollow positive meniscus, is arranged distally behind an entry window 14a. The entrance lens 14b, the deflection unit 14c and the exit lens 14d are connected in a rotationally fixed manner with the shaft 2 or respectively the jacket tube 12.
Subsequent to the distal optical assembly 14, a proximal optical assembly 15 is arranged rotatably within the inner jacket tube, wherein the rotary axis is the central symmetry axis of the endoscope shaft 2. The proximal optical assembly 15 is arranged in a rotatable holder 16 and has two separate lens system channels for a right image and a left image of a stereoscopic image pair. The lens system channels each have, progressing in FIG. 1 from left to right, an aperture 20, a biconvex entrance lens and an achromatic lens group embodied as a doublet. Each of the lens system channels is followed by an image sensor 18.
The entire proximal optical assembly 15 is arranged rotatably in the shaft 2 by means of a coupling element 17, which is connected with the handle 3 and performs rotations of the handle 3 with respect to the shaft 2. A signal cable 19, which ends in an outer signal cable 7 on the end of the handle 3, which can lead for example to an external computer system, is guided through the center of the coupling element 17.
As discussed above, this optical system is affected by stronger 3D distortions, which restrict the usable stereo base.